This invention relates to a cooling disk unit for use in a wafer chucking device.
Generally, in a semiconductor device manufacturing process, an electrical test is performed to check whether or not a semiconductor device (e.g. an integrated circuit) normally operates after the semiconductor device is manufactured on a semiconductor wafer (e.g. a silicon wafer).
When the electrical test is carried out, the semiconductor wafer with the semiconductor device is held by a holder which is called a wafer chucking device to give simulated thermal environment to the semiconductor device. That is, the wafer chucking device holds the semiconductor wafer and heats or cools it. The simulated thermal environment is similar to actual thermal environment in which the semiconductor device will be placed and used.
Formerly, such a test is frequently carried out at relatively high temperature between room temperature and about 150xc2x0 C. Recently, however, the test is increasingly carried out at relatively low temperature between about 10xc2x0 C. and about xe2x88x9250xc2x0 C.
A conventional wafer chucking device has a thick disk shape and comprises a vacuum disk unit or a vacuum chucking unit, an electric heater unit, and a cooling disk unit. The vacuum disk unit, the electric heater unit, and the cooling disk unit are superposed on one another. The vacuum disk unit holds the semiconductor wafer by suction of a vacuum pump connected thereto. The electric heater unit heats the semiconductor wafer through the vacuum disk unit. The cooling disk unit has a passage or tunnel which runs inside thereof to pass a cooling fluid or a heat carrier therethrough. The cooling disk unit is cooled by the cooling fluid and cools the semiconductor wafer through the electric heater unit and the vacuum disk unit.
With this structure, the conventional wafer chucking device can selectively give the relatively high temperature environment or the relatively low temperature environment to the semiconductor wafer as the simulated thermal environment.
However, the cooling disk unit is inefficiently cooled by the cooling fluid and has a low heat transfer rate.
In addition, the cooling disk unit has lack of uniformity in temperature distribution on a main surface on which the electric heater unit is laid.
It is therefore an object of this invention to provide a cooling disk unit having a high heat transfer rate.
It is another object of this invention to provide a cooling disk unit having a uniform temperature distribution on its main surface.
Other objects of this invention will become clear as the description proceeds.
According to an aspect of this invention, a cooling disk unit is for cooling a wafer chucking device by exchanging heat with a cooling fluid passing therethrough and comprises a first heat conducting disk having a plurality of first radial channels which are connected to one another at both first inside ends and first outside ends. The cooling disk exchanges the heat with the cooling fluid flowing inward in the first radial channels. A second heat conducting disk is concentrically disposed on either a top or a bottom of the first heat conducting disk and has a plurality of second radial channels which are connected to one another at both second inside ends and second outside ends. The second radial channels are further connected to the first radial channels at either one of the second inside ends or the second outside ends. The second heat conducting disk exchanges the heat with the cooling fluid flowing outward in the second radial channels.
According to another aspect of this invention, a wafer chucking device comprises a wafer chucking unit for chucking a semiconductor wafer thereon. A cooling disk unit is disposed under the wafer chucking unit to cool the semiconductor wafer through the wafer chucking unit by passing a cooling fluid therethrough. A first heat conducting disk has a plurality of first radial channels connected to one another at both first inside ends and first outside ends. The cooling disk exchanges the heat with said cooling fluid flowing inward in the first radial channels. A second heat conducting disk is concentrically disposed on either a top or a bottom of the first heat conducting disk and has a plurality of second radial channels which are connected to one another at both second inside ends and second outside ends. The second radial channels are further connected to the first radial channels at either one of the second inside ends or the second outside ends. The second heat conducting disk exchanges the heat with the cooling fluid flowing outward in the second radial channels.